This invention relates generally to the control of an automotive transmission or the like. More particularly, it relates to improved shift control apparatus for a multiple speed, sliding gear manual transmission.
In recent years there have been many improvements in automotive drive trains, including improvements relating to control apparatus for shifting manual transmissions. Generally, for transmissions incorporating a plurality of forward speed ratios and a reverse speed ratio, the shift control apparatus provides appropriate crossover positions for the shift stick. Each crossover position selects a shift fork or the like, which may be moved longitudinally to engage either of two speed ratios. In a five-speed and reverse transmission, for example, one crossover position might select the first and second forward speed ratios, another the third and fourth forward speed ratios, and yet another the fifth forward and reverse speed ratios.
Copending U.S. application Ser. No. 968,058 filed Dec. 11, 1978 now U.S. Pat. No. 4,228,693 discloses shift control apparatus wherein a main shift rail is rotatable about its longitudinal axis to four positions for crossover selection. In each crossover position the main shift rail is slidable longitudinally along its axis so as to engage the selected speed ratio. In the first and second positions, the main shift rail is slidable to engage respectively the first or second forward speed ratio and the third or fourth forward speed ratio. In the third and fourth positions, the main shift rail is slidable to engage either the fifth forward or reverse speed ratio.
An auxiliary shift rail is slidable to engage fifth, and a reverse idler gear is slidable to engage reverse. The auxiliary shift rail and the reverse idler gear are coupled with the main shift rail by a linkage mechanism. The linkage mechanism is effective to move the auxiliary shift rail in a gear-engaging direction upon sliding of the main shift rail in one longitudinal direction, while at the same time preventing movement of the reverse idler gear. The linkage mechanism also is effective to slide the reverse idler gear in a gear-engaging direction upon sliding of the main shift rail in th opposite longitudinal direction, while at the same time preventing movement of the auxiliary shift rail.
This linkage mechanism requires two levers arranged in a complicated assembly, and two cam devices which must be precisely coordinated. This results in a linkage mechanism which is complex and expensive. Thus, there remains a need in the art for a simple, inexpensive linkage mechanism which may be incorporated in transmission shift control apparatus of the type disclosed.